Being with you and not being with you is the only way I have to measure time.

The line treats time not as an objective sequence of hours but as something registered through intimacy and absence. “Being with you” becomes a kind of fullness or presence in which time may feel suspended, while “not being with you” marks the return of measurable duration—waiting, longing, and the ache of separation. By making alternation (presence/absence) the only “measure,” the speaker suggests that emotional experience is the true clock: love reorganizes perception so that calendars and clocks are secondary to the rhythms of encounter and loss. The phrasing also echoes Borges’s recurring preoccupation with time as subjective, unstable, and bound to memory.